Space Docking Experiment (SPADEX)

By R Anil Kumar

• The two satellites named ‘Chaser’ and ‘Target’ will be launched into slightly different orbits by a single PSLV-class vehicle with an aim to dock at an altitude of about 700 km

• The two satellites will align precisely at speeds of approximately 28,000 km/h to perform a ‘space handshake’ docking to become a single orbiting entity

• In a major step towards autonomous space technology, the country’s leading space organisation ISRO is developing Space Docking Experiment SPADEX (Space Docking Experiment)

• It is one of ISRO’s most significant steps towards developing autonomous docking technology, crucial for India’s growing space ambitions

• Docking systems allow two spacecraft to connect in orbit, enabling critical operations like assembling space stations, refuelling, or transferring astronauts and cargo

Bengaluru, December 17. The Space Docking Experiment (Spadex), set to be launchedby the end of December 2024, will be India’s first mission to demonstrate autonomous docking technology in space.

The Indian Space Research Organisation (ISRO) is preparing to construct an Indian space station above Earth and is on the brink of taking the first step towards it with the Space Docking Experiment mission.

Spadex mission could catapult India into an elite club of spacefaring nations and will place India alongside the US, Russia, and China.

The Space Docking Experiment (Spadex), set to launch on December 30, 2024, will be India’s first mission to demonstrate autonomous docking technology in space, a critical advancement for complex future space operations.

WHAT IS SPADEX?

Spadex will feature two 400-kg satellites, dubbed “Chaser” and “Target,” launched together aboard a PSLV-class rocket.

Once positioned at an altitude of 700 kilometers, these satellites will carry out a precisely orchestrated rendezvous, culminating in their autonomous docking to form a single, unified unit in orbit.

This manoeuvre is crucial for future projects that require docking capabilities, such as space station assembly, satellite refuelling, and the transfer of astronauts or cargo between spacecraft.

WHY IS IT A BIG DEAL?

If successful, Spadex will place India alongside the US, Russia, and China as one of the few nations capable of docking in space.

This achievement is vital for ISRO’s ambitious roadmap, paving the way for the Chandrayaan-4 mission, which aims to retrieve lunar samples, and the proposed Bharatiya Antariksh Space Station.

Chandrayaan-4 mission will involve launching the Ascender, Descender, Propulsion Module and the Returner, and Transfer Module stacks across two launches, which will then be docked in an elliptical Earth Parking Orbit.

The docking capability could also extend the operational life of geostationary satellites by allowing the replacement of their propulsion units directly in orbit.

The mission also highlights a new era in India’s space sector, featuring a significant contribution from Ananth Technologies, a private Indian company that developed the mission’s satellites.

Spadex embodies the collaborative future of public-private partnerships in India’s expanding space industry.

The success of Spadex could open vast opportunities for India in space exploration, from enabling long-duration human spaceflight and constructing large space structures to potential commercial applications in satellite servicing and space debris management.

Why in the News?

Recently, a Hyderabad-based private firm handed over two 400 kg class satellites to ISRO, which will be part of the Space Docking Experiment (SPADEX) planned at the end of 2024.

About Space Docking

Space docking involves precise connection of two spacecraft, whether manned or unmanned, allowing those to operate as a single unit for critical tasks such as refuelling, repair, and crew exchange.

It enables the construction of cutting-edge facilities (like International Space Station) in orbit and advancing space exploration.

Some spacecraft dock with the International Space Station and others berths with the station.

In Docking, the spacecraft can manoeuvre and attach to the station by itself.

In Berthing, an astronaut uses the station’s robotic arm to capture the spacecraft. Then Mission Control takes control from the ground and directs the arm to manoeuvre the spacecraft to the attachment site.

About Space Docking experiment (SPADEX)

ISRO’s SPADEX is a technology demonstration experiment aimed at mastering autonomous docking, a critical capability that only a select few countries (the US, Russia, and China) have.

The two satellites named ‘Chaser’ and ‘Target’ will be launched into slightly different orbits by a single PSLV-class vehicle with an aim to dock at an altitude of about 700 km.

They will align precisely at speeds of approximately 28,000 km/h to perform a ‘space handshake’ docking to become a single orbiting entity.

These satellites will perform complex manoeuvres, including:

Autonomous Rendezvous and Docking: The spacecraft must autonomously navigate, approach, and securely dock while coordinating with each other.

Formation Flying: Demonstrating precise orbital control to maintain relative positions, a key skill for future in-space assembly and satellite servicing.

Remote Operations: The mission will experiment with controlling one spacecraft using the Attitude Control System of the other in docked configuration.

Additionally, it will explore the use of robotic arm technologies for in-space manipulation and servicing.

Significance for India

Space Exploration: SPADEX focuses on scalable and cost-effective docking technology developed in India, essential for India’s space exploration ambitions such as

Gaganyaan for human space flight,

Chandrayaan-4 for lunar sample returns,

BharatiyaAntariksha Station (BAS) for permanent infrastructure in outer space, etc.

Private Sector Participation: Marks a milestone in private sector participation, enabled by space sector reforms like IN-SPACe.

This is the first instance of complete satellite integration by a private company to be used by the ISRO.

Future Impact: Enables international collaboration opportunities for building space infrastructure and deep space exploration along with earning crucial foreign exchange.

Other Potential Applications: Longevity of Geostationary Satellites, future interplanetary missions (such as Mars), assembling space solar stations for generating electricity from the Sun, etc.

Challenges

Complex Docking Mechanism: Satellites travelling at immense speeds (about 8-10 km per second) requires precise communication and coordination for docking.

Any errors in the navigation and control system can result in collision or failure to dock as seen recently in the Sunita Williams’ case.

Automated Systems: Autonomous complex manoeuvres in real-time is technologically challenging due to various dynamic factors such as relative speeds and trajectories.

Sensor Reliability: The sensors used for docking (e.g., cameras, LIDAR, and radar) can face difficulties in the harsh environment of space.

Other challenges: Space debris threat, microgravity effects, data transfer and communication stability, etc. must also be considered at the planning stage.

Conclusion

The development of advanced space technologies by India represents a significant leap forward in space exploration capabilities. Such advancements reflect the nation’s commitment to scientific and technological self-reliance and its aspirations to be a frontrunner in global space research and development, in line with the Atmanirbhar Bharat vision.